title: Purification, crystallization and preliminary crystallographic studies of SPCI-chymotrypsin complex at 2.8 A resolution.
abstract: A binary complex of the Schizolobium parahyba chymotrypsin inhibitor (SPCI) with chymotrypsin was purified by size-exclusion chromatography and crystallized by the sitting-drop vapour-diffusion method with 100 mM MES-NaOH pH 5.5, 20%(w/v) PEG 6000, 200 mM LiCl as precipitant and 200 mM nondetergent sulfobetaine molecular weight 201 Da (NDSB-201) as an additive. SPCI is a small protein with 180 amino-acid residues isolated from S. parahyba seeds and is able to inhibit chymotrypsin at a 1:1 molar ratio by forming a stable complex. X-ray data were collected to 2.8 A resolution from a single crystal of the SPCI-chymotrypsin binary complex under cryogenic conditions. The crystal belongs to space group P2(1)2(1)2(1), with unit-cell parameters a = 45.28, b = 64.57, c = 169.23 A, and the R(merge) is 0.122 for 11 254 unique reflections. A molecular-replacement solution was found using the preliminary crystal structure of SPCI and the structure of chymotrypsin (PDB code 4cha) independently as search models.
authors.affiliation: Biophysics Laboratory, Biological Sciences Institute, University of Brasília, Brasília-DF, 70910-900, Brazil.
authors.forename: Adelson Joel
authors.initials: AJ
authors.lastname: da Silva
authors.forename: Rozeni Chagas Lima
authors.initials: RC
authors.lastname: Teles
authors.forename: Gisele Ferreira
authors.initials: GF
authors.lastname: Esteves
authors.forename: Camila Ramos
authors.initials: CR
authors.lastname: dos Santos
authors.forename: João Alexandre Ribeiro Gonçalves
authors.initials: JA
authors.lastname: Barbosa
authors.forename: Sonia Maria
authors.initials: SM
authors.lastname: de Freitas
mesh_terms: D002852:Chromatography, Ion Exchange; D002918:Chymotrypsin / Q000737:chemistry* / Q000378:metabolism; D003460:Crystallization; D018360:Crystallography, X-Ray / Q000379:methods; D008970:Molecular Weight; D010940:Plant Proteins / Q000737:chemistry*
chemical_list: C096591:Chymotrypsin inhibitor protein, Schizolobium parahybum; D010940:Plant Proteins; D002918:Chymotrypsin